This paper introduces a new concept for the identification of automatic transmission gear trains. It describes the use of kinematic graphs to separate the topological structure of the gear train from its function. Using this method, it has been shown that known epicyclic automatic transmission gear trains can be classified in a systematic and unbiased manner. This procedure allows transmission mechanisms which have different gear arrangements to be compared on a uniform basis so their similarities and differences can be identified.
It has been shown previously that there are 80 non-isomorphic displacement graphs from which all of the six-link, one-degree-of-freedom gear trains can be constructed. Here we show that there are seven non-isomorphic displacement graphs from which all epicyclic-type automatic transmission gear trains with up to six links and with four or more coaxial links can be derived.
In this paper, epicyclic-type transmission gear trains were searched, and their corresponding schematic and graph representations were classified. We found that the known transmission gear trains with six links all belong to these seven displacement graphs.